• Assign permission in the document upload process depending on which department should have access to this document
• Depending on which department a user belongs and also what permission the user has, the view of the document library should be filtered to the documents the user has access to rather than showing everything.
If you want to set a permission based on column, it's best to eliminate that column, and put it into folders instead to make a true level of security. Then uninherit the permissions for each folder, to make permission changes to it.
Then assign a view that, in the folder section, "Displays all items inside folders", to be able to have a user view only what he/she has access to.
Ideally we can't set permission in column level, but we can do a work around. We can have a custom form and using jquery we can hide/show the columns depending on the permission level we can set. Using jquery you can check which group the user belongs and then depending on the user permission hide or show the field/s.
-Vikram
